Kinetic modeling and sensitivity analysis for higher ethanol production in self-cloning xylose-using Saccharomyces cerevisiae.

We constructed a xylose-utilizing Saccharomyces cerevisiae strain using endogenous xylose-assimilating genes (strain K7-XYL). Such self-cloning yeast is expected to make a great contribution to cost reduction of ethanol production processes. However, it is difficult to modify self-cloning yeast for optimal performance because the available gene source is limited.

Xylose fermentation by Saccharomyces cerevisiae using endogenous xylose-assimilating genes.

Objectives: To genetically engineer Saccharomyces cerevisiae for improved ethanol productivity from glucose/xylose mixtures.

Results: An endogenous gene cassette composed of aldose reductase (GRE3), sorbitol dehydrogenase (SOR1) and xylulose kinase (XKS1) with a PGK1 promoter and a terminator was introduced into two S. cerevisiae strains, a laboratory strain (CEN.

Desulfurization of 2,4,6,8-tetraethyl dibenzothiophene by recombinant Mycobacterium sp. strain MR65.

Recombinant Mycobacterium sp. strain MR65 harboring dszABCD genes was used to desulfurize alkyl dibenzothiophenes (Cx-DBTs) in n-hexadecane. The specific desulfurization activity for 2,4,6,8-tetraethyl DBT (C8-DBT) by DszC enzyme was about twice that for 4,6-dipropyl DBT (C6-DBT).

Residue 345 of dibenzothiophene (DBT) sulfone monooxygenase is involved in C-S bond cleavage specificity of alkylated DBT sulfones.

Rhodococcus erythropolis IGTS8 that possesses dibenzothiophene sulfone monooxygenase mutated at residue 345 (Q345A), can degrade octyl sulfide on which the wild strain cannot grow. Residue 345 and the neighbouring residues were changed by site-directed mutagenesis. Only DszA changed at residue 345 gave an altered C-S bond cleavage pattern of 3-methyl DBT sulfone.